Liquid spray nozzle



Sept. 27, 1960 R. G. GRUNDMAN 2,954,172

LIQUID SPRAY NozzLE Filed sept. 1o, 1958 INVENTOR.

BY Z

LIQUID SPRAY NOZZLE Richard G. Grundman, Grand Rapids, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Sept. 10, 1958, Ser. No. 760,133

2 Claims. (Cl. 239-4443) This invention relates to liquid spray nozzles and more particularly to nozzles of the type having plural flow such nozzles are provided with separate low and high capacity flow passages leading to the spray tip, the high capacity flow passage having a spring-biased piston valve to keep it closed in the low flow range. The back side of the piston valve is conventionally vented to atmosphere or to the combustion chamber and considerable pumping effort is required to maintain it full open at the maximum rate of ilow.

It is an object of the invention to realize the maximum rate of flow with less pumping effort.

`Other objects of the invention will be apparent from the drawings and ensuing description.

In the drawings:

Figure 1 is a sectional View along the axis of a liquid spray nozzle incorporating the invention; and Figure 2 is an enlargement of the spray tip portion of Figure l. Referring to the drawings, the liquid `fuel nozzle has an outer housing with an inner chamber 12 that ret paths to accommodate a Wide flow range.

i A typical `nozzle of this type is utilized to spray 'fuel in a gas turbine combustion chamber. In order to achieve good atomization of the fuel at high and low ow rates,

ceives fuel at various rates of flow from an inlet 14 which connects to the usual fuel pump. High and low capacity spray tips 16 and 18 are mounted at one end of the chamber 12 to provide a fuel atomizing outlet for the nozzle. A cap 20 closes off the other end of the chamber 12 and secures a lter 22. An inner housing 24 is mounted in the outer housing 10 by a threaded portion 26 which is longitudinally slotted at 28 to allow fuel to pass tothe spray tip 16.

A valve housing 30 is received in the spray tip end of the inner housing 24 and mounts a reciprocal piston valve ,32. A radial passage 34 in the valve housing 30 transmits fuel -from the chamber 12 to a chamber 36 on the inlet side of a valve seat 38. The piston valve 32 has a tapered pin 40 which is movable in the valve seat 38 to control flow to the high capacity spray tip 16. From a chamber 42 in a flow distribution plug 44 on the outlet side of the valve seat 38, fuel is led to a high capacity swirl chamber 46 by way of a passage 48, an annular chamber 50 and a plurality of tangentially directed passages 52. A discharge orice 54 for the high capacity fuel ilow is formed by the concentric spray tips 16 and 18 to receive fuel from the swirl chamber 46.

A bushing 56 is retained in the inner housing 24 by a threaded plug 58 and is provided with a restricted flow area or venturi-shaped passage 60 which communicates with the chamber 12 by way of a passage 62 in the bushing. From the venturi passage 60 lel is led to a chamber 62 behind the spray tip 18 by a passage 64 in the inner housing 24, a passage 66 in the valve housing 30 and a passage 68 in the 110W distribution plug 44. A swirl plug 70 is retained in the low capacity spray tip 18 by a coil spring 72 and forms a swirl chamber 74 which receives fuel from ICC the chamber 62 by way of a slotted passage 76, an annular chamber 78 and a plurality of tangential passages 80. The swirl chamber 74 feeds a low capacity discharge orifice 82 in the spray tip 18. The tip end of the nozzle may be provided with the usual air director cap 84 to aid atomization.v

From the foregoing it is seen that fuel is ejected from the spray tip 18 by way of the passages 80, 76, 68, 66, 64, 60 and 62 whenever fuel is supplied to the inlet 14 at any rate of ow. In order to achieve good atomization at low rates of ow the swirl passages are necessarily small land the aforesaid overall flow passage system is accordingly a low ow capacity system. The swirl passages 52 of the spray tip 16 are substantially larger than the swirl passages 80 and a high flow capacity passage system is accordingly formed by the passages 52, 48, 34 and 28 which feed the spray tip 16. Higher pressures and higher rates of iiow are required to obtain good atomization from the larger spray tip 16, hence its flow passage system is closed at the lower pressures and flow rates by the piston valve 32.

In order to close the piston valve 32, a compression spring 86 is received in a valve vent chamber 88 in the bushing 56 to engage one end of the valve and urge it in closing direction. A nut 90 is threaded on a post 92 to provide spring force adjustment. 'Ihe piston valve 32 has a face area 94 which is exposed to the inlet pressure of the high flow capacity passage system and another face area 96 which is exposed to the static pressure in the chamber 88. In the usual fuel nozzle the chamber 88 is vented to atmosphere or to the combustion chamber in order that the fuel pressure acting on the face area 94 can overcome the spring 86 and move the piston valve 32 in opening direction. The invention provides a different means of venting the chamber 88 which results in improved nozzleperformance at high flow rates.

In accordance with the invention the low flow capacity passage system Was provided with a reduced area or venturi portion 60 and the chamber 83 is vented to the static pressure of the Venturi throat 98 by a passage 100. The pressure on the face area 96 of the piston valve 32 thus varies in accordance with the rate of flow through the spray tip 18. At low rates of flow the pressure on the face area 96 is but slightly less than the pressure on the face area 94 and the spring 86 is especially effective in maintaining the piston valve 32 closed. As the pressures and flow rates increase to a high level, the static pressure drop in the venturi throat 98 is reflected in the chamber 88 and the reduced pressure on the face area 96 thus augments the increased pressure on the face area 94 to move the piston valve 32 against the spring 86. Less pumping elort at the maximum flow rate is thus required to maintain the valve open than would be the case if the chamber 88 were vented directly to atmosphere or to the combustion chamber.

While the embodiment of the invention here described is preferred, it is understood that modifications may be made by the exercise of skill in the art which will lie within the scope of the invention.

I claim:

l. In a liquid fuel spray nozzle of the duplex flow type having an inlet and an outlet connected by separate high and ylow flow passages, means for supplying liquid fuel to the inlet at various rates of ow, the low flow passage providing constant communication between the inlet and outlet and having a restricted area portion therein, a piston valve for controlling flow through the high flow passage, one side of the piston valve being exposed to the static pressure of the restricted area of the one passage and the other side of the piston valve-being exposed to the pressure in the other flow passage, and a spring engaging and biasing the piston valve in a direction to reduce ow through the other flow passage.

2. A liquid fuel spray nozzle of the duplex flow type comprising a low capacity flow passage having an inlet and a spray tip outlet and a venturi throat therebetween, a high capacity flow passage having an inlet and a spray tip outlet, means for supplying liquid fuel to both inlets at various flow rates, a piston Valve for controlling flow through the high capacity flow passage, one side of the piston valve being exposed to the static pressure of the Venturi throat of the low capacity ilow passage and the other side of the piston valve being exposed to the pres- 4 sure in the high uapacty ow passage, and a spring engaging and biasing the piston valve in a direction to reduce ow through the high capacity flow passage.

References Cited in the le of this patent UNITED STATES PATENTS 

